This invention relates to a humidifier, and more particularly to a self-contained humidifer which supplies steam that is free of bacteria, etc., and which automatically flushes sediment from the steam generating apparatus.
Over the years a wide variety of devices have been proposed for adding humidity to the air flowing through homes, offices, factories, and the like. One class of these devices may be characterized as non-heated. These devices operate by withdrawing water from a reservoir and directing the water into the moving air stream for evaporation thereby. One problem involved in the operation of devices of this type is that they tend to become clogged with sediment resulting from the evaporation process, and therefore must be cleaned regularly in order to assure efficient operation. Another problem involves the fact that such devices tend to pass bacteria and other potentially harmful microorganisms which may be received with the water directly into the air stream. The latter is particlarly undesirable in the case of hospitals, nursing homes, and similar applications.
Another type of prior art humidifier comprises heated devices. Often devices of this type utilize the heated products of combustion flowing from a furnace as a heat source. This heat is utilized to vaporize water flowing through a coil into steam, and the steam is in turn injected into the moving air stream. A significant problem that is encountered with the operation of devices of this type involves the fact that the furnace must be operating in order to provide a heat source. These devices are also similar to non-heated humidifiers in that they tend to become clogged with sediment, and in that they tend to pass bacteria or other microorganisms received in the water into the moving air stream.
The present invention comprises a novel humidifier which overcomes the foregoing and other problems long since associated with the prior art. In accordance with the broader aspects of the invention, an electric heating coil and a water receiving/steam generating coil are mounted in a steam generation zone within a housing. The electric heating coil functions to vaporize water passing through the water receiving/steam generating coil into steam by raising the temperature within the steam generation zone from the ambient temperature to an operating temperature which is sufficiently high to kill bacteria and other microorganisms entering the humidifier with the water. The water receiving/steam generating coil is formed from material which substantially expands as the temperature within the steam generation zone is raised to the operating temperature, and which subsequently substantially contracts as the steam generation zone cools following de-actuation of the electric heating coil. The expansion and contraction of the water receiving/steam generating coil dislodge sediment tending to accumulate therein, and the dislodged sediment is flushed from the coil with the fluid flowing therethrough.
Fluid flowing from the water receiving/steam generating coil together with any sediment carried thereby is discharged into the upper portion of a sediment separation zone in the housing. Steam is in turn directed from the upper portion of the sediment separation zone into the plenum chamber of an associated air handling apparatus. Sediment together with any unvaporized water flowing from the water receiving/steam generating coil are received in the lower portion of the sediment separation zone under the action of gravity. A drain apparatus extending into the lower portion of the sediment separation zone functions as a syphon to periodically withdraw excess liquids accumulated therein.
The humidifier operates under the regulation of an electrical control circuit. The circuit includes a temperature responsive switch which operates the electric heating coil through cycles of actuation and de-actuation each having a predetermined time duration to maintain the operating temperature within the steam generation zone. Water is admitted to the water receiving/steam generating coil through a solenoid-operated valve which is controlled by a slow-to-release relay.
The release time of the slow-to-release relay is longer than the operating cycles of the electric heating coil, so that water continuously flows through the water receiving/steam generating coil during the operation of the humidifier. Water also flows through the coil for a predetermined time following the termination of operation of the electric heating coil to cool the water receiving/steam generating coil and to flush sediment therefrom. The electric control circuit further includes a temperature responsive switch mounted in the steam generation zone which functions to actuate the fan of the associated air handling apparatus whenever the humidifier is operating to supply humidity.